The article considers the influence of the structure of polymer-cement plaster coating on the nature of its destruction during the operation of the wall structure. It was shown that the use of purposefully selected components of the mixture (RPP, polymer fiber, cellulose ethers, fine aggregate with a low modulus of elasticity, etc.) made it possible to increase the uniformity of its structure and contact area with masonry, reduce the number of cracks during hardening, and slow down their development during operation, increase the durability of it and the wall structure. The durability of the wall structure largely depends on the number of defects in the plaster coating and the contact area between it and the masonry.

The article rethinks the approach to the development of compositions of plaster mortar as the load on the plaster coating located on the 1st or 24th floor of the building differs significantly. To solve the problem within the framework of existing concepts, principles and regulatory requirements are not possible, as they are applicable to the solutions used in low-rise building. To achieve this goal, it is necessary to develop the scientific basis for the design of plaster mortar. In order to do that, it is necessary to analyze the processes occurring in the plaster coating when it is applied and hardened, the knowledge of the mechanism of the destruction of the "masonry - plaster coating" system, and the calculation and evaluation of stresses. The designated physical and mechanical parameters and the selected plaster mortar compositions should ensure the "work" of the system at the maximum level of such stresses.

Увеличение объемов высотного строительства, применение новых стеновых материалов требует переосмысления подхода к проектированию составов штукатурных растворов. Это вызвано тем, что нагрузки на штукатурное покрытие, находящееся на 1 или 24 этажах здания, значительно отличаются. Решить поставленную задачу в рамках существующих представлений, принципов и нормативных требований невозможно, так как они применимы для растворов, применяемых при малоэтажном строительстве. Для достижения поставленной цели в данной статье разработана научная основа проектирования составов штукатурных растворов для высотных зданий. А для этого проведен анализ процессов, протекающих в штукатурном покрытии при его нанесении и твердении, механизма разрушения системы кладка штукатурное покрытие . Выявлены и проанализированы на примерах и графиках основные причины развития трещин, такие как температурные и влажностные деформации штукатурного покрытия и кладки и их разность, напряжения, вызванные ими, воздействие влаги, льда и агрессивных веществ. Для того чтобы предотвратить разрушение штукатурного покрытия, рассчитали величины физико-механических характеристик (прочность при сжатии и изгибе, модуль упругости и др.), с учетом напряжений в нем и контактной зоне с кладкой, возникающие при твердении раствора и деформации стеновой конструкции. Сформулированы принципы и критерии, при которых будет обеспечена долговечность штукатурного покрытия и стеновой конструкции. Рекомендованы составляющие и подобраны два состава раствора, которые позволили увеличить водоудерживающую способность смеси, уменьшить усадку штукатурного покрытия при твердении, уменьшить количество трещин, возникающих при твердении, и предотвратить или замедлить их развитие.The increase the volume of the high-rise construction, the use of new wall materials, requires a rethinking of the approach to the design of plaster mortar compositions. This is due to the fact that the load on the plaster coating, located on the 1 or 24 floors of the building, are significantly different. To solve the problem within the framework of existing concepts, principles and regulatory requirements is not possible, as they are applicable to solutions used in low-rise construction. To achieve this goal, the scientific basis for the design of plaster mortar compositions for high-rise buildings was developed in this article. An analysis of the processes occurring in the plaster coating during its application and hardening, the destruction mechanism of the system masonry - plaster coating was carried out. The main reasons for the development of cracks, such as temperature and moisture deformations of the plaster coating and masonry and their difference, the stresses caused by them, exposure to moisture, ice and aggressive substances, were identified and analyzed using examples and graphs. In order to prevent the destruction of the plaster coating, the values of physical and mechanical characteristics (compressive and bending strength, elastic modulus, etc.) were calculated, taking into account the stresses in it and the contact zone with the masonry, arising from the hardening of the mortar and the deformation of the wall structure. The principles and criteria are formulated under which the durability of the plaster coating and wall structure will be ensured. For two compositions of the mortar, which allowed to increase the water-holding ability of the mixture, reduce the shrinkage of the plaster coating during hardening, reduce the number of cracks that occur during hardening and prevent or slow down their development, the components were recommended and selected.

High-rise construction volume increase and new wall materials use require changing the approach to the design of plastermortar compositions. The analysis has showed that it is possible to reduce the number of cracks in the plaster coating by increasingthe water holding capacity of the mortar mixture. To optimize the prescription parameters of the mortar mixture, thefive-factor experiment with fine aggregate and the filler with a low modulus of elasticity, disperse polymeric powders andcellulose ethers, a polymer fiber for microdispersed reinforcement has been used. The obtained data indicate that the proposedapproach enables to obtain plaster mortars with physic mechanical characteristics that provide optimal working conditions“masonry - plaster coatings”.

To create the optimal composition of the plaster solution with the preassigned properties, it is necessary to know the processes taking place in the “masonry-coating” system, including in the contact zone between it and the masonry, the mechanism of its destruction. The purpose of the presented work was to describe the processes of occurrence and growth of cracks in the plaster coating and its contact zone with the masonry, in the process of its application, hardening and operation of the wall structure. In recent years, significant progress has been made in analyzing the reliability of plaster coatings, their behavior during operation, however, there are problems in predicting the evolution of damage in terms of initiation and growth of cracks, which ultimately leads to cracking and delamination of the plaster coating from masonry. The behavior of the plaster coating largely depends on its structure and the structure of the contact zone. The state of the “masonry-coating” system was described and this made it possible to obtain data on the process of its destruction, the appearance and spread of cracks. The system was destroyed according to two main schemes: formation and development of cracks in the coating and in the contact zone. Thus, these researches make it possible to reduce the number of defects in the contact zone with the masonry and increase the service life of the wall structure.